1. Field of the Invention
The present invention relates generally to digital broadcasting transmission and reception systems. More particularly, the present invention pertains to a digital broadcasting transmission system capable of improving performance of a reception system by inserting a hidden pilot signal and a signal processing method thereof, and also a corresponding digital broadcasting reception system and a signal processing method thereof.
2. Description of the Related Art
FIG. 1 is a schematic block diagram of the United States 8-VSB DTV transmission system. The transmission system includes a forward error correction (FEC) encoder 110, a sync insertion unit 120, a pilot insertion unit 130, a pulse shaping filter 140, and a radio frequency (RF) unit 150.
The FEC encoder 110 includes a randomizer 111, a Reed-Solomon (RS) encoder 113, an interleaver 115, and a trellis encoder 117.
The randomizer 111 randomizes an incoming MPEG2-TS data packet. The RS encoder 113 assigns a RS parity of certain bytes for the error correction of data. The interleaver 115 interleaves the RS-encoded data according to a certain pattern. The trellis encoder 117 trellis-encodes the interleaved data at a 2/3 rate.
The sync insertion unit 120 inserts a segment sync and a field sync into the FEC-encoded signal. The pilot insertion unit 130 inserts a pilot tone by applying a certain DC component to data symbol of 8 levels. The pulse shaping filter 140 pulse-shapes the pilot-tone-inserted signal by use of a filter having a certain roll-off factor. The RF unit 150 up-converts the pulse-shaped signal into a signal of a RF channel band to be transmitted, and transmits the converted signal via an antenna.
FIG. 2 is a structure of a transmission frame containing the segment sync and the field sync which are inserted in the sync insertion unit 120 of FIG. 1.
The final data frame is created in a manner that an output signal from the FEC encoder 110 is mapped into a signal of 8 levels, that is, −7, −5, −3, −1, 1, 3, 5, 7, and the segment sync and field sync having a binary PN sequence of −5 and 5 levels are added to the 8-level signal.
Still referring to FIG. 2, each segment sync consists of four symbols and a whole segment including the segment sync signal consists of 832 symbols. 313 segments make up a frame, and a first segment of each frame consists of a series of a PN sequence which is the field sync.
The PN sequence is a sync known to a reception side, and is used as a reference signal for equalization.
The conventional digital broadcasting transmission system is vulnerable to the multipath environment. Accordingly, performance of a reception system depends on that of an equalizer which removes ghost components occurring in the multipath.
However, the performance degrades since the frequency of the field sync signal, which is used by the equalizer as the reference signal, is too low as shown in FIG. 2.
The more frequently the reference signal is inserted, the more likely the performance of the equalizer improves. However, the insertion frequency of the field sync in the received signal is limited since data transmission rate decreases as much as the insertion frequency increases.